This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-277670 filed Sep. 13, 2001 and Japanese Patent Application No. 2002-126718 filed Apr. 26, 2002.
1. Field of the Invention
The present invention relates to an engine starter mounted on a vehicle that has an automatic system to turn off the engine by suspending fuel supply to the engine when some predetermined conditions are met while the vehicle is running, for instances, in a constant running or in a decelerating running.
2. Description of Related Art
Conventionally, there has been a system to suspend fuel supply to the engine to reduce fuel consumption when some predetermined conditions are met while a vehicle is in a constant running or in a decelerating running. However, such a system suspends the fuel supply only when the number of the engine revolutions is within a predetermined range. If the engine revolutions fall below the predetermined range, the system resumes the fuel supply to prevent an engine stall. In this case, the engine under suspension of the fuel supply has to maintain certain revolutions to get restarted by itself when the fuel supply is resumed. Therefore, there has been a limit to the reduction of fuel consumption.
On the other hand, the engine has to be restarted by an engine starter when the fuel supply has been suspended in order to reduce the fuel consumption further until the engine revolutions fall into the range where the engine is not able to get restarted by itself by resuming of the fuel supply.
However, a pinion-plunging type starter, which is popular as an engine starter, is not able to start the engine while the engine is revolving. Therefore, the pinion-plunging type starter restarts the engine after the engine stops its revolution. As a result, starting response of the engine is not satisfactory.
Given the factors, as one of the engine starters that enables restarting of the engine during it is revolving, such a starter is known that starts the engine through a means for transmitting power such as a belt, as is disclosed in the U.S. Pat. No. 5,959,385 for instance.
The above engine starter has a one-way clutch to prevent an overrun of an armature, an excessive rotation of the armature forced by the engine, because a driving shaft outputting rotation of a motor is linked continuously with a crankshaft of the engine through a belt. In order to prevent the overrun of the armature, the one-way clutch breaks the power transmission by cutting off the linkage between the driven side (the driving shaft side) and the driving side (the motor side) if the rotation of the driven side surpasses the rotation of the driving side, after the engine starts.
However, if the number of the engine revolutions in which the one-way clutch is disconnected is below the lower limit of the engine revolutions above which the engine is able to get restarted by itself by resuming of the fuel supply, there exists a range where the engine is not able to get restarted by itself, nor by the starter. In this case, the engine has to wait to get restarted until the engine revolutions fall enough for the one-way clutch to get connected and to transmit power. Therefore, the engine still has a disadvantage in respect to the starting response.
It is therefore an object of the present invention to provide an engine starter able to start an engine quickly even in a range where the engine under suspension of fuel supply is not able to get restarted by itself by resuming of the fuel supply.
An engine starter according to an embodiment of the present invention comprises a motor to generate a rotating force to start the engine and a power transmission structure to transmit the rotation of the motor to a crankshaft of the engine through a clutch.
The clutch is set so that an upper limit of engine revolutions below which a driving member and a driven member are able to change from a disconnected state to a connected state surpasses a lower limit of the engine revolutions above which the engine under suspension of fuel supply is able to get restarted by itself by resuming of the fuel supply in a decreasing process of the engine revolutions. The upper limit of the engine revolutions below which the driving member and the driven member are able to change from a disconnected state to a connected state is referred to as the connecting rotation number (Nc) hereafter. The lower limit of the engine revolutions above which the engine under suspension of fuel supply is able to get restarted by itself by resuming of the fuel supply is referred to as the minimum rotation number for a self-restart (Nmin) hereafter.
In this construction, when the engine is to be restarted, for instance, to accelerate the vehicle after the fuel supply is stopped, the engine is able to get restarted by itself by resuming of the fuel supply if the number of the engine revolutions has been ensured enough for the engine to get restarted by itself by resuming of the fuel supply.
In addition, the engine is able to get restarted by the engine starter before the number of the engine revolutions falls to Nmin, since Nc is set above Nmin as is explained above. Therefore, the engine is restarted quickly even in the range where the engine under suspension of the fuel supply is not able to get restarted by itself by resuming of the fuel supply. As a result, a high starting response is ensured.